This robust fence in front of a historic Georgetown home is likely made from hundreds of recycled Revolutionary War firearms.

In the basement of the U.S. Capitol Building is a hidden storage room full of ornate floor tiles leftover from the 1850s.

The institution is sitting on a goldmine of 21,000 paints, varnishes, pigments, and primers preserved for posterity.

The privately owned cemetery that holds room for Washington's finest when they step down from life.

Perhaps the most scandalous statue of America's first president.

The oldest continuously operating fish market in the United States.

When it opened during the final years of the embargo, all the drinks and cigars were free.

An Industrial Revolution-era public work that purified water using nothing but sand.

Fittingly, America's museum of architecture is itself a magnificently designed old building.

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

Enormous piles of historically significant stones, dumped by Congress in a forest, and abandoned for 60 years.

This grand gothic brewery has been pumping out suds for over a hundred years.

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

Franciscan monks created a facsimile of the Holy Land for North Americans who couldn’t afford the trip overseas.

The United States Capitol's former columns still stand.

The oldest restaurant in the world is this old-world Spanish eatery, still known for its suckling pig.

This fairy-tale, neo-Gothic church in the Azores is a world of magical realism.

A completely underwater art museum sends a stark message about humans' impact on the environment.

Volcanic rocks ground down into sand make this Spanish beach as black as night.

A 16th-century Andalusian palace.

The world's largest wooden structure.

The final resting place of the great navigator, or maybe his brother.

Sleepy fishing port not included on many maps.